Mold surface of a concrete block



FIG. 1 is a perspective view of a molded surface of a concrete product, according to our new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a right side elevational view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a top view thereof; and,

FIG. 6 is a bottom view thereof.

The broken lines in all views are included for the purpose of illustrating portions of the concrete product that form no part of the claimed design. 

The ornamental design for a mold surface of a concrete block, as shown and described. 